Study Note on Weld Overlay Processes for Composite Wear-Resistant Materials

Literature Overview

This paper by Zhang Wanhong, Gong Weimin, and Liang Shankun from the School of Materials Science and Engineering at Henan University of Science and Technology, published in Mining Machinery in 2012, investigates the fabrication of composite wear-resistant materials through weld overlay processes. The study is particularly significant for engineers in the mining, cement, and aggregate processing industries where equipment components such as crusher liners, conveyor rollers, and pump impellers are subjected to severe abrasive and impact loading conditions. The research bridges the gap between metallurgical theory and practical process development for extending component service life through surface hardening.

Core Technical Viewpoints

The authors explore multiple weld overlay techniques including submerged arc welding (SAW), shielded metal arc welding (SMAW), and flux-cored arc welding (FCAW) for depositing hardfacing alloys onto steel substrates. Key technical viewpoints include:

The selection of overlay alloy composition must be matched to the specific wear mechanism encountered in service, whether it is abrasion, impact, or a combination thereof.
Multi-layer overlay strategies can combine a bond layer (for metallurgical compatibility with the substrate) with a wear layer (for surface hardness and wear resistance), optimizing both bonding integrity and surface performance.
The dilution effect from the base metal is a critical factor that must be managed through appropriate heat input control, pre-heating strategies, and layer thickness planning.
Post-weld heat treatment can significantly influence the final hardness and microstructure of the overlay layer, particularly for martensitic hardfacing alloys where tempered martensite provides an optimal balance of hardness and toughness.

Comparison of Overlay Processes for Wear-Resistant Applications

Process	Typical Hardness (HV)	Dilution Control	Productivity	Cost
SAW	400–600	Moderate	High	Low
SMAW	450–700	Poor	Low	Low
FCAW	400–650	Moderate	High	Moderate
GTAW	500–800	Good	Low	Moderate
PTA	600–1000	Excellent	Moderate	High
Laser Cladding	700–1200	Excellent	Moderate	High

Process Development and FMEA Analysis

Applying a Failure Mode and Effects Analysis (FMEA) approach to the weld overlay process for wear-resistant materials reveals the following critical failure modes:

Failure Mode	Severity	Occurrence	Detection	Risk Priority	Mitigation
Overlay cracking	9	5	6	270	Pre-heat; reduce heat input; use low-carbon bond layer
Spalling/delamination	8	4	7	224	Control dilution; ensure substrate cleanliness; use graded composition
Insufficient hardness	6	6	5	180	Verify alloy composition; control cooling rate; apply PWHT
Excessive distortion	7	5	4	140	Use balanced welding sequences; back-plate support; stress-relief annealing
Inclusion defects	5	7	6	210	Clean flux/wire; control shielding gas; pre-dry consumables

Engineering Practice Integration

In mining machinery applications, the practical implementation of composite wear-resistant overlay layers follows a systematic approach:

Component assessment: Determine the dominant wear mechanism through field analysis (abrasive, adhesive, erosive, or impact wear).
Alloy selection: Choose the overlay alloy based on wear mechanism matching (e.g., carbide-based alloys for abrasive wear, martensitic alloys for impact-abrasive wear, oxide-based alloys for high-temperature wear).
Process qualification: Conduct weld procedure qualification per NB/T 47014 or ASME IX to establish reproducible process parameters.
Substrate preparation: Machine the base surface to remove scale and oxide; ensure surface roughness of Ra 6.3–12.5 μm for optimal bonding.
Overlay deposition: Apply the bond layer first (typically 1–2 mm of low-dilution alloy), followed by the wear layer (2–5 mm of hardfacing alloy).
Post-processing: Grind the overlay surface to specified profile; apply stress-relief annealing at 550–650°C if required by the alloy specification.
Quality verification: Perform hardness mapping across the overlay surface; conduct visual inspection for surface defects; verify thickness by ultrasonic measurement.

Key Technical Parameters for Hardfacing Alloys

Alloy Type	Typical Composition	As-Welded Hardness	After Tempering	Wear Mechanism Suitability
High-carbon martensitic	2.5–4.5% C, 5–8% Cr	550–650 HV	500–600 HV	Impact-abrasive
Carbide-forming	10–20% Cr, 3–5% C, Mo, V	700–900 HV	650–850 HV	Abrasive
High-chromium white iron	14–22% Cr, 2–3.5% C	800–1000 HV	750–950 HV	Severe abrasive
Ceramic composite	WC, TiC, Cr3C2 in Fe/Ni matrix	1000–1500 HV	900–1400 HV	Extreme abrasive

Study Insights and Implications

The paper effectively demonstrates that the performance of weld overlay composite wear-resistant materials is not solely determined by the alloy composition but is equally influenced by process parameters and post-processing. A critical insight for practitioners is that the bond layer composition must be carefully designed to bridge the thermal expansion mismatch and metallurgical incompatibility between the base steel and the hardfacing alloy. For example, when applying a high-chromium white iron wear layer onto a low-carbon steel substrate, an intermediate layer of austenitic stainless steel or a nickel-based alloy significantly reduces the risk of interfacial cracking during service. The study also highlights the importance of process repeatability in production environments, where automation of welding parameters is essential for maintaining consistent overlay quality across large batches of components. Engineers should also consider the economic balance between overlay thickness and component life extension, as excessive overlay thickness increases cost and may introduce unnecessary thermal distortion without proportional improvement in wear life.